Sensibilidad de los ciclones extratropicales a los flujos superficiales sobre los hielos marinos

Con el fin de conocer mejor los mecanismos básicos que contribuyen al desarrollo de las tormentas extratropicales del hemisferio sur, se intenta determinar el rol del hielo marino y del océano como forzantes externos. El hielo reduce el intercambio de calor entre la superficie y la atmósfera, y además afecta el flujo superficial de cantidad de movimiento. Estudiar el impacto de la parametrización de estos procesos tiene un interés adicional dado que en la región subantártica, gran parte de los modelos numéricos, operativos y de investigación, no tienen un buen desempeño. Utilizando un modelo regional de alta resolución, en el que están incluidos todos los procesos físicos presentes en la atmósfera, se realizaron estudios numéricos de sensibilidad, modificando distintas condiciones que afectan los flujos superficiales. Para el estudio se seleccionaron dos tormentas que ocurrieron cerca de la Península Antártica a comienzos de setiembre de 1987. El primer ciclón se desarrolló rapidamente en el Pacífico Sur Oriental, al producirse la interacción de una perturbación en el jet subtropical con una onda en el jet polar. El segundo ciclón, un desarrollo sucesivo y corriente abajo del anterior, se formó sobre el Mar de Weddell. El modelo simuló exitosamente la formación de ambos ciclones, con todos los detalles que los caracterizan. No obstante, existe un déficit de energía cinética respecto al análisls y las bajas son menos profundas. Estas tormentas producen un gran transporte meridional de calor, característico de los sistemas baroclínicos, pero la débil cortante vertical del viento que presentan señala la presencia de una componente barotrópica. Las condiciones previas a ambos ciclones indicaban que el flujo era internamente inestable en las latitudes en que ocurrieron los desarrollos posteriores. Estas tormentas alcanzaron un rápido desarrollo sobre zonas en las que los flujos superficiales de calor sensible y latente eran muy pequeños. Los flujos de calor sobre el hielo marino dependen fundamentalmente del espesor con que se parametriza la capa de hielo. El flujo superficial de cantidad de movimiento depende, entre otros factores, de la rugosidad de la superficie. El modelo asume un espesor del hielo y una rugosidad (tanto del océano como de la banquisa) que resultan excesivos comparados con las observaciones, Los estudios de sensibilidad muestran que los forzantes de superficie juegan un rol secundario en el desarrollo de estos ciclones. Los flujos superficiales de calor producen un impacto negativo, ya que tienden a disminuir la baroclinicidad de los sistemas (calientan la zona con advección fría). AI permitir el libre intercambio de calor en la superficie de la banquisa, se obtiene principalmente una disminución del gradiente de presión en superficie cerca del centro de los sistemas y una leve disminución de la energía cinética en toda la tropósfera. Si bien los flujos de calor tienen poco impacto durante la etapa de rápida profundización de estos ciclones, el calentamiento que se produce en el borde de la banquisa contribuye a crear las condiciones de inestabilidad necesarias para que una posterior tormenta pueda desarrollarse en esa región. La reducción de la altura de la rugosidad conduce a una intensificación de las tormentas. Si bien en algunos experimentos la respuesta fue poco significativa, al reducir la rugosidad del hlelo y/o del océano, la presión a nivel del mar y la distribución vertical de la energía cinética estuvieron más cerca del análisis. En otros experimentos, al eliminarse los flujos superficiales de cantidad de movimiento, la atmósfera responde de inmediato con un considerable crecimiento de la energía cinética a través de toda la tropósfera en la zona del jet. Los resultados sugieren que las simulaciones de las tormentas subantárticas pueden ser mejoradas reduciendo la altura de la rugosidad sobre hielo marino y sobre el océano en zonas de fuertes vientos.Fil:Menéndez, Claudio Guillermo. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Treatment with tocilizumab or corticosteroids for COVID-19 patients with hyperinflammatory state: a multicentre cohort study (SAM-COVID-19)

Objectives: The objective of this study was to estimate the association between tocilizumab or corticosteroids and the risk of intubation or death in patients with coronavirus disease 19 (COVID-19) with a hyperinflammatory state according to clinical and laboratory parameters. Methods: A cohort study was performed in 60 Spanish hospitals including 778 patients with COVID-19 and clinical and laboratory data indicative of a hyperinflammatory state. Treatment was mainly with tocilizumab, an intermediate-high dose of corticosteroids (IHDC), a pulse dose of corticosteroids (PDC), combination therapy, or no treatment. Primary outcome was intubation or death; follow-up was 21 days. Propensity score-adjusted estimations using Cox regression (logistic regression if needed) were calculated. Propensity scores were used as confounders, matching variables and for the inverse probability of treatment weights (IPTWs). Results: In all, 88, 117, 78 and 151 patients treated with tocilizumab, IHDC, PDC, and combination therapy, respectively, were compared with 344 untreated patients. The primary endpoint occurred in 10 (11.4%), 27 (23.1%), 12 (15.4%), 40 (25.6%) and 69 (21.1%), respectively. The IPTW-based hazard ratios (odds ratio for combination therapy) for the primary endpoint were 0.32 (95%CI 0.22-0.47; p < 0.001) for tocilizumab, 0.82 (0.71-1.30; p 0.82) for IHDC, 0.61 (0.43-0.86; p 0.006) for PDC, and 1.17 (0.86-1.58; p 0.30) for combination therapy. Other applications of the propensity score provided similar results, but were not significant for PDC. Tocilizumab was also associated with lower hazard of death alone in IPTW analysis (0.07; 0.02-0.17; p < 0.001). Conclusions: Tocilizumab might be useful in COVID-19 patients with a hyperinflammatory state and should be prioritized for randomized trials in this situatio

Impact of COVID-19 on cardiovascular testing in the United States versus the rest of the world

Objectives: This study sought to quantify and compare the decline in volumes of cardiovascular procedures between the United States and non-US institutions during the early phase of the coronavirus disease-2019 (COVID-19) pandemic. Background: The COVID-19 pandemic has disrupted the care of many non-COVID-19 illnesses. Reductions in diagnostic cardiovascular testing around the world have led to concerns over the implications of reduced testing for cardiovascular disease (CVD) morbidity and mortality. Methods: Data were submitted to the INCAPS-COVID (International Atomic Energy Agency Non-Invasive Cardiology Protocols Study of COVID-19), a multinational registry comprising 909 institutions in 108 countries (including 155 facilities in 40 U.S. states), assessing the impact of the COVID-19 pandemic on volumes of diagnostic cardiovascular procedures. Data were obtained for April 2020 and compared with volumes of baseline procedures from March 2019. We compared laboratory characteristics, practices, and procedure volumes between U.S. and non-U.S. facilities and between U.S. geographic regions and identified factors associated with volume reduction in the United States. Results: Reductions in the volumes of procedures in the United States were similar to those in non-U.S. facilities (68% vs. 63%, respectively; p = 0.237), although U.S. facilities reported greater reductions in invasive coronary angiography (69% vs. 53%, respectively; p < 0.001). Significantly more U.S. facilities reported increased use of telehealth and patient screening measures than non-U.S. facilities, such as temperature checks, symptom screenings, and COVID-19 testing. Reductions in volumes of procedures differed between U.S. regions, with larger declines observed in the Northeast (76%) and Midwest (74%) than in the South (62%) and West (44%). Prevalence of COVID-19, staff redeployments, outpatient centers, and urban centers were associated with greater reductions in volume in U.S. facilities in a multivariable analysis. Conclusions: We observed marked reductions in U.S. cardiovascular testing in the early phase of the pandemic and significant variability between U.S. regions. The association between reductions of volumes and COVID-19 prevalence in the United States highlighted the need for proactive efforts to maintain access to cardiovascular testing in areas most affected by outbreaks of COVID-19 infection

A first update on mapping the human genetic architecture of COVID-19

peer reviewe

EXPLORANDO TEMPERATURAS MÁXIMAS Y MÍNIMAS EN DIFERENTES REANÁLISIS. PARTE 1: CAMPOS MEDIOS ESTACIONALES

Con la motivación de que a menudo se emplean reanálisis para estudiar el clima regional aun cuando no es clara la magnitud de sus errores, en este artículo se explora la incertidumbre inherente a utilizar datos de reanálisis de temperatura máxima y mínima en el sudeste de Sudamérica. Se comparan campos medios observacionales de TX (verano) y TN (invierno) (Tencer y otros, 2011), tres diferentes reanálisis multidecádicos (NCEP, ERA40 y 20CR) y cuatro modelos climáticos regionales (LMDZ, PROMES, RCA y REMO). El reanálisis más aceptable para representar el campo medio de TX es ERA40, mientras que NCEP es el más aceptable para TN. El error del ensemble de reanálisis presenta magnitudes similares para ambas variables (errores menores a 4oC), pero la dispersión entre los reanálisis individuales es mayor en verano. La mayor dispersión entre reanálisis se encuentra en el centro de la Argentina en esa estación. Se analizó también el balance de energía en superficie para los diferentes reanálisis, encontrándose que los procesos intervinientes en este balance impactan directamente sobre la temperatura. Los errores en la temperatura están, por lo tanto, en parte vinculados con errores en la determinación de los flujos de calor sensible y latente así como de la radiación neta. La capacidad de los reanálisis y de los modelos regionales para representar la distribución geográfica de TX y TN se analizó mediante diagramas de Taylor. Los ensembles de reanálisis o de modelos regionales suelen tener mejores estadísticos en estos diagramas que los reanálisis o modelos individuales. Además, los estadísticos exhibidos en los diagramas de Taylor sugieren que los errores en la distribución geográfica de las anomalías espaciales de temperatura tienen una magnitud similar para los reanálisis y para los modelos regionales analizados

Downscaling extreme month-long anomalies in southern South America

International audienceWe investigate the performance of one stretched-grid atmospheric global model, five different regional climate models and a statistical downscaling technique in simulating 3 months (January 1971, November 1986, July 1996) characterized by anomalous climate conditions in the southern La Plata Basin. Models were driven by reanalysis (ERA-40). The analysis has emphasized on the simulation of the precipitation over land and has provided a quantification of the biases of and scatter between the different regional simulations. Most but not all dynamical models underpredict precipitation amounts in south eastern South America during the three periods. Results suggest that models have regime dependence, performing better for some conditions than others. The models' ensemble and the statistical technique succeed in reproducing the overall observed frequency of daily precipitation for all periods. But most models tend to underestimate the frequency of dry days and overestimate the amount of light rainfall days. The number of events with strong or heavy precipitation tends to be under simulated by the models. © The Author(s) 2009

Performance of a multi-RCM ensemble for South Eastern South America

International audienceThe ability of four regional climate models to reproduce the present-day South American climate is examined with emphasis on La Plata Basin. Models were integrated for the period 1991-2000 with initial and lateral boundary conditions from ERA-40 Reanalysis. The ensemble sea level pressure, maximum and minimum temperatures and precipitation are evaluated in terms of seasonal means and extreme indices based on a percentile approach. Dispersion among the individual models and uncertainties when comparing the ensemble mean with different climatologies are also discussed. The ensemble mean is warmer than the observations in South Eastern South America (SESA), especially for minimum winter temperatures with errors increasing in magnitude towards the tails of the distributions. The ensemble mean reproduces the broad spatial pattern of precipitation, but overestimates the convective precipitation in the tropics and the orographic precipitation along the Andes and over the Brazilian Highlands, and underestimates the precipitation near the monsoon core region. The models overestimate the number of wet days and underestimate the daily intensity of rainfall for both seasons suggesting a premature triggering of convection. The skill of models to simulate the intensity of convective precipitation in summer in SESA and the variability associated with heavy precipitation events (the upper quartile daily precipitation) is far from satisfactory. Owing to the sparseness of the observing network, ensemble and observations uncertainties in seasonal means are comparable for some regions and seasons

Optimization of adsorptive removal of α-toluic acid by CaO2 nanoparticles using response surface methodology

The present work addresses the optimization of process parameters for adsorptive removal of α-toluic acid by calcium peroxide (CaO2) nanoparticles using response surface methodology (RSM). CaO2 nanoparticles were synthesized by chemical precipitation method and confirmed by Transmission electron microscopy (TEM) and high-resolution TEM (HRTEM) analysis which shows the CaO2 nanoparticles size range of 5–15 nm. A series of batch adsorption experiments were performed using CaO2 nanoparticles to remove α-toluic acid from the aqueous solution. Further, an experimental based central composite design (CCD) was developed to study the interactive effect of CaO2 adsorbent dosage, initial concentration of α-toluic acid, and contact time on α-toluic acid removal efficiency (response) and optimization of the process. Analysis of variance (ANOVA) was performed to determine the significance of the individual and the interactive effects of variables on the response. The model predicted response showed a good agreement with the experimental response, and the coefficient of determination, (R2) was 0.92. Among the variables, the interactive effect of adsorbent dosage and the initial α-toluic acid concentration was found to have more influence on the response than the contact time. Numerical optimization of process by RSM showed the optimal adsorbent dosage, initial concentration of α-toluic acid, and contact time as 0.03 g, 7.06 g/L, and 34 min respectively. The predicted removal efficiency was 99.50%. The experiments performed under these conditions showed α-toluic acid removal efficiency up to 98.05%, which confirmed the adequacy of the model prediction